An improved method for purification of DNA polymerase alpha from mouse myeloma has been developed. The method involves gentle homogenization in an isotonic buffer at pH 7.6 and then centrifugation at 100,000 x g; the supernatant fraction is adjusted to pH 6.0 and chromatographed on CM-sepharose, then DEAE-sepharose, and finally oligo(dT)-cellulose. Alpha-polymerase is obtained in near homogenous form in three days with a recovery of about 20%. The effect of purified myeloma DNA binding proteins upon the activity of the purified alpha-polymerase is under investigation. In addition a protein factor has been identified that stimulates the enzyme as it replicates single-stranded calf thymus DNA. This factor appears distinct from the typical DNA binding proteins isolated on DNA-cellulose columns. BIBLIOGRAPHIC REFERENCES: Kuff, E.L., Lueders, K.K., Orenstein, J., and Wilson, S.H.: Differential response of type-C and intracisternal type-A particle markers in cells treated with Iododeoxyuridine and Dexamethasone. J. of Virology 19: 709-716, 1976. Matsukage, A., Sivarajan, M., and Wilson, S.H.: Studies on DNA alpha-polymerase of mouse myeloma: Partial purification and comparison of three molecular forms of the enzyme. Biochemistry 15: 5305-5314, 1976.